Koinophilia
It makes biological sense that sexual creatures should be attracted to mates sporting a predominance of common or average features, as opposed to extraordinary features. Natural selection results, over the course of generations, in beneficial (or "fit") features replacing their disadvantageous counterparts. Thus, natural selection causes beneficial features to become increasingly more common with each generation, while the disadvantageous features become increasingly rare. A sexual creature, therefore, wishing to mate with a fit partner, would be expected to avoid individuals sporting unusual, peculiar, unique or uncommon features (many of which are likely to be due to mutations), while being especially attracted to those individuals displaying a predominance of common or average features. This term is coined as "koinophilia".
Read more about this topic: Averageness